MORE white Americans will fight and possibly die in any conflict in Iraq than at any time since the Vietnam war, despite the fact that a disproportionate number of blacks still join the armed services to escape poverty and unemployment.

A study by Northwest University in Illinois shows that while a high number of black recruits enlist to learn trades that will give them a post-military career in computers or administration, whites from the lower end of the economic spectrum tend to end up in frontline units like the infantry.

Charles Moskos, a military sociologist at the university, said yesterday: ''If anyone ends up complaining about battlefield deaths this time, it'll be poor rural whites. They're the new generation 'grunts', the majority behind the basic bayonet.''

During the US military's involvement in Vietnam, black power militants claimed, quite accurately, that more of their ethnic kin were put in harm's way in frontline combat than was justified by their share of population.

Blacks continue to serve in disproportionate numbers. They still make up 20% of the military establishment, but only 12% of the ethnic mix. The difference is that they volunteer for fewer battlefield jobs.

Of the army's 45,586 combat infantry, just 10.6%, and only 245 of the air force's 12,000 pilots - 2% - are black. The navy's carrier-borne air wings have a mere 2.5% non-white fliers.

Special forces show an even greater divide. A total of 196 of the 4278 Green Berets come from the black community.

Saudi border guards, meanwhile, yesterday arrested a Kuwaiti believed responsible for killing one American and critically wounding another in an ambush near a US military base, the official Saudi Press Agency reported.

The agency quoted an unidentified Saudi Interior Ministry official as saying the Kuwaiti, who was not named, was arrested early yesterday wile ''sneaking into Saudi Arabia from Kuwait''.